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The removal of bombs, shells and other explosives from thousands of acres on the banks of the Raritan River is about to enter its final stage. Brian Thompson reports. (Published Friday, Jun 1, 2012)

Updated at 10:08 AM EDT on Monday, Jun 4, 2012

Explosives technicians working for the U.S. Army Corps of Engineers are in the final stages of a military ordinance cleanup on the site of the old Raritan Arsenal in Edison, N.J.

"You always have to look down to make sure you're not stepping on places," said Bob Selfridge, who is in charge of mapping for the Corps.

In a cleanup now in its 26th year, the Corps finally has state-of-the-art technology to speed up the search.

A remote-controlled tractor pulls a sledge that pulses electromagnetic signals into the ground, finding any metallic anomalies below.

And there's lot to find.

In a quarter of a century, technicians have found nearly 400 shells, bombs or other potential explosives and destroyed them on-site.

They've also found more than 200,000 pounds of metals, everything from shell casings to gas masks to fire extinguishers.

They date back to 1917, when the then-War Department was in a hurry to establish a trans-shipping point to supply the American Expeditionary Force that was sailing to France to join the Allies.

Its continued role in World War II left a legacy of discarded ordnance that is only being removed in the past two decades or so.

"By their nature, military munitions are dangerous, no matter how old or how decrepit they are," said Sandra Piettro, project manager for the Corps.

In all, there were 2,000 acres that had to be investigated and cleaned, and now there are just under 100 acres left, according to Piettro.

But that includes what could be the toughest job, some 2,000 linear feet of rotting wharf and the waters of the Raritan River underneath where the ammunition was loaded onto ships heading to the European battlefields.

Piettro says investigation of that area, most of it underwater, will begin this summer.

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